Apparently my 3-31 posting didn't catch an eye as I got no response. My instrument and dash lights went out on fuse circuit 21(the exterior lights on this circuit are ok). I removed the rheostat module from the instrument circuit board and could not continuity between the red and blue wires with the rheostat turned in all positions. Is this the way to check this module? I hate to committ $150 for a new one if it isn't. If anyone has dealt with this, please share your experience. Thanks.

Yes, that sounds like the rheostat failed but you should be able to bypass teh rheo by connecting the two appropriate wires and restore instrument lights. Do you really need the dimmer function? Is that worth $150? Anyway, you could get one in a salvage yard car for 1% of that cost I bet.

Agreed. bypassing the rheostat is the most logical approach. My concern is the apparently complex electronics in the module for both ground circuit and the wiper circuit that varies the light intensity. Do you know anyone who has done this on the Volvo module?

Eh? Hrm. As far as I know, all a rheostat is a variable resistor. In other words, voltage goes up and down based on which way you've turned it. As such, you can bypass the rheostat just by connecting the two wires together and altogether skipping the rheostat. Or go to the junk yard. Or try and pick one up from radioshack or a special electronics store that matches the resistance and wattage rating of the volvo rheostat. Obviously if you do my last suggestion it won't look so nice, but it's cheaper than an expensive part from Volvo.

Me, I would just bypass it. I never dim my lights.
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'